[Show abstract][Hide abstract] ABSTRACT: Myelodysplastic syndromes (MDS), clonal hematopoietic stem-cell disorders mainly affecting older adult patients, show ineffective hematopoiesis in one or more of the lineages of the bone marrow. Most MDS are characterized by anemia, and a number of cases progresses to acute myeloid leukemia (AML). Indeed, the molecular mechanisms underlying the MDS evolution to AML are still unclear, even though the nuclear signaling elicited by PI-PLCβ1 has been demonstrated to play an important role in the control of the balance between cell cycle progression and apoptosis in MDS cells. Here we review both the role of epigenetic therapy on PI-PLCβ1 promoter and the changes in PI-PLCβ1 expression in MDS patients treated for anemia.
[Show abstract][Hide abstract] ABSTRACT: The existence and function of inositide signaling in the nucleus is well documented and we know that the existence of the inositide cycle inside the nucleus has a biological role. An autonomous lipid-dependent signaling system, independently regulated from its plasma membrane counterpart, acts in the nucleus and modulates cell cycle progression and differentiation.We and others focused on PLCβ1, which is the most extensively investigated PLC isoform in the nuclear compartment. PLCβ1 is a key player in the regulation of nuclear inositol lipid signaling, and, as discussed above, its function could also be involved in nuclear structure because it hydrolyses PtdIns(4,5)P2, a well accepted regulator of chromatin remodelling. The evidence, in a number of patients with myelodysplastic syndromes, that the mono-allelic deletion of PLCβ1 is associated with an increased risk of developing acute myeloid leukemia paves the way for an entirely new field of investigation. Indeed the genetic defect evidenced, in addition to being a useful prognostic tool, also suggests that altered expression of this enzyme could have a role in the pathogenesis of this disease, by causing an imbalance between proliferation and apoptosis. The epigenetics of PLCβ1 expression in MDS has been reviewed as well.
No preview · Article · Oct 2010 · Advances in enzyme regulation
[Show abstract][Hide abstract] ABSTRACT: Lamin A is a nuclear envelope constituent involved in a group of human disorders, collectively referred to as laminopathies, which include Emery-Dreifuss muscular dystrophy. Because increasing evidence suggests a role of lamin A precursor in nuclear functions, we investigated the processing of prelamin A along muscle differentiation. Both protein levels and cellular localization of prelamin A appears to be modulated during C2C12 mouse myoblasts activation. Similar changes also occur in the expression of two lamin A-binding proteins: emerin and LAP2α. Furthermore prelamin A forms a complex with LAP2α in differentiating myoblasts. Prelamin A accumulation in cycling myoblasts by expressing unprocessable mutants affects LAP2α and PCNA amount and increases caveolin 3 mRNA and protein levels, whilst accumulation of prelamin A in differentiated muscle cells following treatment with a farnesyl transferase inhibitor inhibits caveolin 3 expression. These data provide evidence for a critical role of lamin A precursor in the early steps of muscle cell differentiation. In fact the post-translational processing of prelamin A affects caveolin 3 expression and influences the myoblast differentiation process. Thus, altered lamin A processing could affect myoblast differentiation and/or muscle regeneration and might contribute to the myopathic phenotype.
No preview · Article · Oct 2010 · Advances in enzyme regulation
[Show abstract][Hide abstract] ABSTRACT: Venerina (little Venus) is the name given to a wax model representing a pregnant young woman that was created in Florence (Italy) by Clemente Susini (1754-1814) in 1782. It is currently located in the historic Science Museum of the University of Bologna. The model was constructed so as to enable removal of the thoracic and abdominal walls and various organs, exposing the heart, diaphragm and an opened uterus with a well-developed fetus. The woman is small, about 145 cm (4' 9') tall and of delicate build; she looks like a teenage girl. We know that Clemente Susini worked directly with the cadaver and copied the anatomical preparation exactly. This artist often represented the true structure using a wax mould; the existence of two other versions of this specimen suggests that this model was made in this way. Therefore, Venerina's body may be a faithful representation of a young woman who died while pregnant. Observation of the body confirms that the organs are normal, except for the heart and great vessels. The walls of both ventricles are of equal thickness and the ventricles themselves of approximately equal size. The arch of the aorta and the enlarged pulmonary trunk are connected by a short duct about 3.5 mm in diameter. If this structure represents an open arterial duct, we can deduce that the two ventricles worked under the same conditions of blood pressure, hence their equal wall thickness. If the young woman died from this congenital disease, the cause of death has been diagnosed on a wax model of her body after more than two centuries.
Full-text · Article · Oct 2009 · Journal of Anatomy
[Show abstract][Hide abstract] ABSTRACT: Collagen VI is an ECM protein which forms a prominent microfibrillar network in the endomysium of skeletal muscle. Mutations in the genes coding for the three chains of collagen VI cause skeletal muscle diseases; the severe wasting Ullrich congenital muscular dystrophy (UCMD) normally present at birth, and the milder Bethlem myopathy (BM). The pathogenesis of both collagen VI myopathies was unknown until 2003. Our group, utilizing Col6a1 deficient mice, discovered a latent mitochondrial dysfunction that caused increased apoptosis in muscle cells. These effects could be reverted by incubating Col6a1 null muscle fibres with cyclosporin A (CsA), an inhibitor of the mitochondrial permeability pore; more interestingly, the treatment of Col6a1 null mice with CoA rescued the muscle phenotype in vivo. These findings demonstrated an unexpected collagen VI/mitochondrial connection as the basis for the UCMD and BM pathogenesis and suggested a strategy for a possible pharmacological treatment of the diseases. This was assessed by demonstrating that muscle biopsies from patients with UCMD showed an abnormal mitochondrial depolarization and that treatment with CsA normalized the mitochondrial phenotype. In this study we report the results of an open pilot trial of four UCMD and one BM patients, representing a range of collagen VI deficiency and having mutations in three of the collagen VI genes. As determined in muscle biopsies prior to treatment, all patients displayed mitochondrial dysfunction and muscle fibres showed an increased frequency of apoptosis. When patients were treated for 1 month with a low daily dose of CsA, primary muscle cell cultures of biopsies obtained at the end of the treatment showed a decreased apoptosis and increased immunohistochemical signs of muscle fibre regeneration. These results confirm that the pathogenic mechanism found in Col6a1 deficient mice also plays a crucial role in hereditary muscle diseases in human, and suggest that targeted treatment of these mitochondrial defects in patients with UCMD and BM may be effective in preventing and/or reverting muscle alterations. It is also important to consider that desensitization of the permeability transition pore by CsA occurs independently of calcineurin inhibition; because a CsA derivative that has no immunosuppressive activity appears to be as effective as the parent molecule, long-term trials should be designed to prevent irreversible muscle damages in young patients affected by collagen VI myopathies, without exposing them to infective risks.
No preview · Article · Feb 2009 · Advances in enzyme regulation
[Show abstract][Hide abstract] ABSTRACT: The nucleus of eukaryotic cells contains all the information needed for cell proliferation and differentiation, however the initiation of these programmes are dependent on the signalling pathway elicited by different agonists. The existence of a nuclear phosphoinositide signalling stems from the early evidence that isolated nuclei posses the lipid kinases capable of phosphorylating phosphatidylinositol (PI) and phosphatidylinositol 4-phosphate (PIP). The synthesis of phosphatidylinositol 4,5- phosphate (PIP2) was clearly increased only in the nuclear fraction from Friend cells terminally differentiated towards erythrocytes (Cocco et al., 1987). On the contrary its amount along with that of PIP was decreased in nuclei of Swiss 3T3 cells stimulated to grow with insulin-like growth factor-I (IGFI) (Manzoli et al., 1989). Following these early observations we and others have demonstrated in several cell type the participation of the whole phosphoinositide cycle in the nucleus (Cocco et al., 1994; Martelli et al., 1992; Divecha et al., 1991; Martelli et al., 1994; Mazzoni et al., 1992). Here we review the most recent achievements on this issue.
No preview · Article · Jan 2009 · European journal of histochemistry: EJH
[Show abstract][Hide abstract] ABSTRACT: The regulation of the hematopoietic stem cell pool size and the processes of cell differentiation along the hematopoietic lineages involve apoptosis. Among the different factors with a recognized activity on blood progenitor cells, TRAIL - a member of the TNF family of cytokines - has an emerging role in the modulation of normal hematopoiesis.PKC(epsilon) levels are regulated by EPO in differentiating erythroid progenitors and control the protection against the apoptogenic effect of TRAIL. EPO-induced erythroid CD34 cells are insensitive to the apoptogenic effect of TRAIL between day 0 and day 3, due to the lack of specific surface receptors expression. Death receptors appear after day 3 of differentiation and consequently erythroid cells become sensitive to TRAIL up to day 9/10, when the EPO-driven up-regulation of PKC epsilon intracellular levels inhibits the TRAIL-mediated apoptosis, via Bcl-2. In the time interval between day 3 and 9, therefore, the number of erythroid progenitors can be limited by the presence of soluble or membrane-bound TRAIL present in the bone marrow microenvironment.
Full-text · Article · Jan 2009 · European journal of histochemistry: EJH
[Show abstract][Hide abstract] ABSTRACT: membrane-free nuclei were capable of synthesizing polyphosphoinositides (Cocco et al., 1987) and that some agonists induced changes of inositide metabolism at the nuclear but not at the cytoplasmic level (Martelli et al., 1992), the question arised of the precise localization of this signaling system within the nucleus (Irvine and Divecha, 1992). In fact, it appeared of fundamental interest to determine whether the inositides and the related enzymes are restricted to the nuclear envelope membranes, or localized at DNA-containing structures. In the first case, the system could represent an extension of the transduction system located at the cell membrane, in the second, it could be autonomous and involved in the regulation of genomic functions.
No preview · Article · Jan 2009 · European journal of histochemistry: EJH
[Show abstract][Hide abstract] ABSTRACT: The understanding of a common complex phenotype such as insulin resistance can be favored by evaluation of monogenic syndromes. Clinical definition, pathogenesis, and therapeutic strategies for the insulin resistance syndrome can thus be improved by the characterization at the molecular genetic level of monogenic forms of lipodystrophies. Among them, the Dunnigan-type familial partial lipodystrophy (FPLD), the mandibuloacral dysplasia (MADA), the syndromes of partial lipodystrophy with cardiomyopathy, the Hutchinson-Gilford progeria (HGPS), and the atypical Werner's syndrome (WS) are due to mutations of the gene coding for the nuclear lamin A/C. FPLD has been shown to associate with altered processing of the lamin A precursor protein, known as prelamin A. The molecular mechanism causing the lipodystrophy phenotype downstream of prelamin A accumulation resides in an anomalous interaction of the nuclear lamina protein with the transcription factor sterol regulatory element binding protein 1 (SREBP1), which slows down the nuclear import of SREBP1. The ultimate effect of sustained prelamin A accumulation in adipocytes is a reduced transcription and possibly activation of the transcription factor peroxisome proliferator-activated receptor (PPARγ) which is involved in differentiation. In the present study, we show that prelamin A accumulates in the nucleus and establishes a strong interaction with SREBP1. We further investigate the interplay between SREBP1 and farnesylated, non-farnesylated or pathogenic prelamin A forms in transfected adipocytes. The obtained results support the view of a major role of prelamin A accumulation in the pathogenesis of LMNA-linked adipose tissue disorders. Furthermore, we found that treatment with the PPARγ ligand troglitazone (TZD) is able to rescue the adipogenic program. Since FPLD recapitulates the essential metabolic abnormalities of the common insulin resistance syndrome, the beneficial effects of TZD on monogenic lipodystrophies might provide a clue as to the future treatment strategies also for the common syndrome of insulin resistance.
No preview · Article · Dec 2007 · Advances in enzyme regulation
[Show abstract][Hide abstract] ABSTRACT: Mast cells are important elements of the body response to foreign antigens, being those represented either by small molecules (allergic response) or harbored by foreign microorganisms (response to parasite infection). These cells derive from hematopoietic stem/progenitor cells present in the marrow. However, in contrast with most of the other hematopoietic lineages, mast cells do not differentiate in the marrow but in highly vascularized extramedullary sites, such as the skin or the gut. Mast cell differentiation in the marrow is activated as part of the body response to parasites. We will review here the mast cell differentiation pathway and what is known of its major intrinsic and extrinsic control mechanisms. It will also be described that thrombopoietin, the ligand for the Mpl receptor, in addition to its pivotal rule in the control of thrombocytopoiesis and of hematopoietic stem/progenitor cell proliferation, exerts a regulatory function in mast cell differentiation. Some of the possible implications of this newly described biological activity of thrombopoietin will be discussed.
No preview · Article · Jul 2007 · Annals of the New York Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Signal transduction from plasma membrane to cell nucleus is a complex process depending on various components including lipid signaling molecules, in particular phosphoinositides and their related enzymes, which act at cell periphery and/or plasma membrane as well as at nuclear level. As far as the nervous system may concern the inositol lipid cycle has been hypothesized to be involved in numerous neural as well as glial functions. In this context, however, a precise panel of glial PLC isoforms has not been determined yet. In the present experiments we investigated astrocytic PLC isoforms in astrocytes obtained from foetal primary cultures of rat brain and from an established cultured (C6) rat astrocytoma cell line, two well known cell models for experimental studies on glia. Identification of PLC isoforms was achieved by using a combination of RT-PCR and immunocytochemistry experiments. While in both cell models the most represented PI-PLC isoforms were beta4, gamma1, delta4, and epsilon, isoforms PI-PLC beta2 and delta3 were not detected. Moreover, in primary astrocyte cultures PI-PLC delta3 resulted well expressed in C6 cells but was absent in astrocytes. Immunocytochemistry performed with antibodies against specific PLC isoforms substantially confirmed this pattern of expression both in astrocytes and C6 glioma cells. In particular while some isoenzymes (namely isoforms beta3 and beta4) resulted mainly nuclear, others (isoforms delta4 and epsilon) were preferentially localized at cytoplasmic and plasma membrane level.
No preview · Article · Mar 2007 · Journal of Cellular Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Lamins A and C, in association with B-type lamins, are the major components of the nuclear lamina, located between the inner nuclear membrane and the chromatin. By interaction with a number of nuclear proteins, lamins are involved in many functions, including nuclear positioning and shape, chromatin organization, and regulation of gene transcription activity. This multi-functional aspect may account for the wide phenotype variety occurring in patients affected by mutations in the lamin A/C gene, which give rise to a growing class of genetic disorders collectively called laminopathies. These diseases (16 distinct disease phenotypes have been reported) can be grouped, on the basis of tissue and organ system involvement, as laminopathies with muscle involvements, neuronal involvements, and metabolic multiorgan involvements leading to premature senescence. Different models have been advanced to find phenotype-genotype associations that could account for the large variability in laminopathies: nuclear fragility, modifications of the nuclear envelope/chromatin relationships, alteration of gene expression, etc. Here we report evidence that, at least in the group of laminopathies with a progeric disease phenotype, LMNA mutations result in the accumulation in the nucleus of unprocessed prelamin A. This, in turn, causes an altered distribution of the lamin B receptor (LBR) and destabilization of two heterochromatin-associated proteins, HP1β and three-methylated histone H3. The resulting heterochromatin and nuclear defects can be also induced in normal cells either by using drugs that interfere with some steps of lamin A post-translational processing, or by transfection with specific LMNA mutations that lead to accumulation of unprocessed prelamin A. These results strongly suggest that the accumulation of farnesylated lamin A precursor elicits a toxic effect that results in irregular nuclear profiles with deep envelope invaginations, loss of peripheral heterochromatin, and reduction of whole transcriptional activity, mainly due to an aberrant accumulation of transcripts. This hypothesis has been confirmed by the possibility of rescuing the structural and functional alterations of progeric nuclei by a drug treatment that destabilizes the accumulated prelamin A. This has been obtained in cell lines obtained from different patients affected by the Hutchinson-Gilford progeria syndrome (HGPS), a severe pre-mature aging disorder which results in the patient death in the second decade. Our results demonstrate that the combined treatment with the farnesyl-transferase inhibitor mevinolin, and the histone deacetylase inhibitor tricostatin A, is able to greatly reduce the accumulation of mutated prelamin A, leading to rescue of the nuclear shape, heterochromatin organization and transcriptional activity in the patient's fibroblasts. These results confirm that, at least in the progeric group of laminopathies, nuclear defects are related to accumulation of unprocessed prelamin A and that they can be rectified by a pharmacological treatment.
No preview · Article · Feb 2007 · Advances in Enzyme Regulation
[Show abstract][Hide abstract] ABSTRACT: Inositol lipid-derived second messengers have long been known to have an important regulatory role in cell physiology. Phosphatidylinositol 3-kinase (PI3K) synthesizes the second messenger 3,4,5'-phosphatidylinositol trisphosphate (Ptdlns 3,4,5P3) which controls a multitude of cell functions. Down-stream of PI3K/PtdIns 3,4,5P3 is the serine/threonine protein kinase Akt (protein kinase B, PKB). Since the PI3K/ PtdIns 3,4,5P3 /Akt pathway stimulates cell proliferation and suppresses apoptosis, it has been implicated in carcinogenesis. The lipid phosphatase PTEN is a negative regulator of this signaling network. Until recently, it was thought that this signal transduction cascade would promote its anti-apoptotic effects when activated in the cytoplasm. Several lines of evidence gathered over the past 20 years, have highlighted the existence of an autonomous nuclear inositol lipid cycle, strongly suggesting that lipids are important components of signaling pathways operating at the nuclear level. PI3K, PtdIns(3,4,5)P3, Akt, and PTEN have been identified within the nucleus and recent findings suggest that they are involved in cell survival also by operating in this organelle, through a block of caspase-activated DNase and inhibition of chromatin condensation. Here, we shall summarize the most updated and intriguing findings about nuclear PI3K/ PtdIns(3,4,5)P3/Akt/PTEN in relationship with carcinogenesis and suppression of apoptosis.
No preview · Article · Feb 2007 · European journal of histochemistry: EJH
[Show abstract][Hide abstract] ABSTRACT: Over the last years, evidence has suggested that phosphoinositides, which are involved in the regulation of a large variety of cellular processes both in the cytoplasm and in the plasma membrane, are present also within the nucleus. A number of advances has resulted in the discovery that phosphoinositide-specific phospholipase C signalling in the nucleus is involved in cell growth and differentiation. Remarkably, the nuclear inositide metabolism is regulated independently from that present elsewhere in the cell. Even though nuclear inositol lipids hydrolysis generates second messengers such as diacylglycerol and inositol 1,4,5-trisphosphate, it is becoming increasingly clear that in the nucleus polyphosphoinositides may act by themselves to influence pre-mRNA splicing and chromatin structure. Among phosphoinositide-specific phospholipase C, the beta(1) isoform appears to be one of the key players of the nuclear lipid signaling. This review aims at highlighting the most significant and up-dated findings about phosphoinositide-specific phospholipase C beta(1) in the nucleus.
No preview · Article · May 2006 · Biochimica et Biophysica Acta
[Show abstract][Hide abstract] ABSTRACT: Protein kinase C (PKC) isozymes constitute a family of ubiquitous phosphotransferases which act as key transducers in many agonist-induced signaling cascades. To date, at least 11 different PKC isotypes have been identified and are believed to play distinct regulatory roles. PKC isoforms are physiologically activated by a number of lipid cofactors. PKC is thought to reside in the cytoplasm in an inactive conformation and to translocate to the plasma membrane or cytoplasmic organelles upon cell activation by different stimuli. However, a sizable body of evidence collected over the last 20 years has shown PKC to be capable of translocating to the nucleus. Furthermore, PKC isoforms are resident within the nucleus. Studies from independent laboratories have to led to the identification of quite a few nuclear proteins which are PKC substrates and to the characterization of nuclear PKC-binding proteins which may be critical for finely tuning PKC function in this cell microenvironment. Several lines of evidence suggest that nuclear PKC isozymes are involved in the regulation of biological processes as important as cell proliferation and differentiation, gene expression, neoplastic transformation, and apoptosis. In this review, we shall highlight the most intriguing and updated findings about the functions of nuclear PKC isozymes.
No preview · Article · May 2006 · Biochimica et Biophysica Acta